From: Wei Liu <wei.liu@kernel.org>
To: Michael Kelley <mikelley@microsoft.com>
Cc: Wei Liu <wei.liu@kernel.org>,
Praveen Kumar <kumarpraveen@linux.microsoft.com>,
"linux-hyperv@vger.kernel.org" <linux-hyperv@vger.kernel.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
KY Srinivasan <kys@microsoft.com>,
Haiyang Zhang <haiyangz@microsoft.com>,
Stephen Hemminger <sthemmin@microsoft.com>,
Dexuan Cui <decui@microsoft.com>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"mingo@redhat.com" <mingo@redhat.com>,
"bp@alien8.de" <bp@alien8.de>, "x86@kernel.org" <x86@kernel.org>,
"hpa@zytor.com" <hpa@zytor.com>,
"viremana@linux.microsoft.com" <viremana@linux.microsoft.com>,
Sunil Muthuswamy <sunilmut@microsoft.com>,
"nunodasneves@linux.microsoft.com"
<nunodasneves@linux.microsoft.com>
Subject: Re: [PATCH] hyperv: root partition faults writing to VP ASSIST MSR PAGE
Date: Tue, 20 Jul 2021 16:29:23 +0000 [thread overview]
Message-ID: <20210720162923.rsbl24v5lujbiddj@liuwe-devbox-debian-v2> (raw)
In-Reply-To: <MWHPR21MB15938E4E72E1A3EB3744AD53D7E29@MWHPR21MB1593.namprd21.prod.outlook.com>
On Tue, Jul 20, 2021 at 04:20:44PM +0000, Michael Kelley wrote:
> From: Wei Liu <wei.liu@kernel.org> Sent: Tuesday, July 20, 2021 6:35 AM
> >
> > On Tue, Jul 20, 2021 at 06:55:56PM +0530, Praveen Kumar wrote:
> > [...]
> > > >
> > > >> + if (hv_root_partition &&
> > > >> + ms_hyperv.features & HV_MSR_APIC_ACCESS_AVAILABLE) {
> > > >
> > > > Is HV_MSR_APIC_ACCESS_AVAILABLE a root only flag? Shouldn't non-root
> > > > kernel check this too?
> > >
> > > Yes, you are right. Will update this in v2. thanks.
> >
> > Please split adding this check to its own patch.
> >
> > Ideally one patch only does one thing.
> >
> > Wei.
> >
>
> I was just looking around in the Hyper-V TLFS, and I didn't see
> anywhere that the ability to set up a VP Assist page is dependent
> on HV_MSR_APIC_ACCESS_AVAILABLE. Or did I just miss it?
The feature bit Praveen used is wrong and should be fixed.
Per internal discussion this is gated by the AccessIntrCtrlRegs bit.
Wei.
>
> Maybe the VP Assist page is not useful for the APIC EOI optimization
> Purposes if !HV_MSR_APIC_ACCESS_AVAILABLE, but the VP Assist
> page has other uses, such as for nested enlightenments. So I
> wonder if the VP Assist page setup really should be gated on
> HV_MSR_APIC_ACCESS_AVAILABLE.
>
> Michael
next prev parent reply other threads:[~2021-07-20 16:31 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-07-19 18:51 [PATCH] hyperv: root partition faults writing to VP ASSIST MSR PAGE Praveen Kumar
2021-07-20 11:20 ` Wei Liu
2021-07-20 13:25 ` Praveen Kumar
2021-07-20 13:35 ` Wei Liu
2021-07-20 16:20 ` Michael Kelley
2021-07-20 16:29 ` Wei Liu [this message]
2021-07-21 4:10 ` Michael Kelley
2021-07-21 7:12 ` Praveen Kumar
2021-07-21 10:10 ` Wei Liu
2021-07-21 11:32 ` Praveen Kumar
2021-07-21 15:07 ` Michael Kelley
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20210720162923.rsbl24v5lujbiddj@liuwe-devbox-debian-v2 \
--to=wei.liu@kernel.org \
--cc=bp@alien8.de \
--cc=decui@microsoft.com \
--cc=haiyangz@microsoft.com \
--cc=hpa@zytor.com \
--cc=kumarpraveen@linux.microsoft.com \
--cc=kys@microsoft.com \
--cc=linux-hyperv@vger.kernel.org \
--cc=linux-kernel@vger.kernel.org \
--cc=mikelley@microsoft.com \
--cc=mingo@redhat.com \
--cc=nunodasneves@linux.microsoft.com \
--cc=sthemmin@microsoft.com \
--cc=sunilmut@microsoft.com \
--cc=tglx@linutronix.de \
--cc=viremana@linux.microsoft.com \
--cc=x86@kernel.org \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox